The present invention relates to graphite holding elements for heating bars in industrial furnaces.
In industrial furnaces, more particularly in protective-atmosphere and vacuum furnaces, graphite heating bars are used as heating elements. Preferably, the heating bars are formed as graphite tubes, which are disposed axially in the direction of the furnace axis and distributed at equal intervals along the furnace circumference. For fastening and for current supply, the heating bars are each held in their central region in a boltable graphite block. This type of fastening has the advantage that, as they heat up, the graphite bars can expand freely toward the end faces of the furnace. The current flows from heating bar to heating bar via fittings formed of either graphite U-tubes or solid graphite members.
In certain types of industrial furnaces, the graphite heating bars must, because of structural and thermal conditions, be fastened at each of their ends, i.e., near the end faces of the furnace chamber. Again, graphite blocks can be used as fastening elements.
Graphite rings or graphite rings divided into several sectors (if the graphite heating bars are connected in parallel) are also used. Blocks and rings provide mechanical fastening as well as electrical supply. However, this causes the heating bars to be firmly clamped at both ends. Thus, the thermal linear expansion of the heating tubs often causes the graphite rings to break.